In magnetic tape cartridges, which are being used as storage media that are employed in external storage units for computers, etc., there is known a type where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case. This magnetic tape is employed to archive data for computers, etc., and stores important information. For this reason, reel-rotation restraining means for restricting rotation of the reel is installed so that problems, such as tape jamming, etc., do not occur and that the magnetic tape is not pulled out of the cartridge case inadvertently when not being used, such as when being stored, etc.
The reel-rotation restraining means is equipped with a reel locking member for restricting rotation of the reel by engaging part of the reel. When the tape cartridge is loaded into a drive unit of an external storage unit, etc., the reel locking member of the reel is unlocked according to the reel chucking operation of the rotation means of the drive unit.
Due to the need for enhanced reliability enhancement in operation of the reel-rotation restraining means, as well as for prevention of the entry of dust into the cartridge case, etc., the reel-rotation restraining means can be separated into a reel locking member for restricting rotation of the reel, an urging member for urging the reel locking member in a locking direction, and an releasing member for moving the reel locking member in an unlocking direction by moving according to the reel chucking operation of the rotation means of the drive unit.
That is, in the inoperative state of the magnetic tape cartridge, the reel is restricted by the reel locking member so that it does rotate unexpectedly. In this manner, the magnetic tape is not pulled out of the magnetic tape cartridge. If the magnetic tape cartridge is loaded into a drive unit, and the reel is chucked by the rotation means of the drive unit, the releasing member is moved and unlocks the reel locking member. In this state, the reel is rotatable and the magnetic tape can be pulled out or rewound.
However, the aforementioned mechanism has the problem that assembly of the releasing member with respect to the reel is troublesome and therefore operability will be reduced. Particularly, providing three leg portions in the releasing member so that the lower ends thereof are inserted through the through holes provided in the reel and the tips thereof are made to abut part of the rotation means of the drive unit, so that they are pushed up and unlock the releasing member by the chucking operation of said rotation means of the drive unit, are advantageous in achieving structural simplification. This structure, however, has the problem that the assembly, which involves inserting the releasing member into the center opening of the reel and then inserting the leg portions into the through holes, cannot be easily performed.
More specifically, in the case where the size of the center opening in the reel is smaller than that of a portion of the cartridge case in which the releasing member is housed, and the releasing member cannot be assembled in a horizontal posture, the assembly operation becomes complicated and troublesome and the operation of forcibly pushing the releasing member is required.
In addition, in the case where the releasing member is assembled by a robot, etc., it is necessary to accurately position and hold the releasing member.
When magnetic tape is forwarded or rewound, the releasing member rotates integrally with the reel at high speeds, but the reel locking member does not rotate. The sliding portions of the two members slide against each other and the temperatures of the sliding portions rise due to frictional heat. Thus, the aforementioned structure has the problem that it is disadvantageous in durability.
The present invention has been made in view of the points mentioned above. Accordingly, it is a first object of the present invention to provide a magnetic tape cartridge where the operation of assembling the releasing member of the reel-rotation restraining means with respect to the reel has been improved.
In magnetic tape cartridges, which are being used as storage media that are employed in external storage units for computers, etc., there is known a type where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case. This magnetic tape is employed to archive data for computers, etc. Since important information has been stored, the magnetic tape cartridge is constructed so that problems, such as tape jamming, etc., do not occur and that the magnetic tape is not pulled out of the cartridge unexpectedly.
In addition, to pull out the magnetic tape, a leader member such as a leader pin, a leader block, etc., is firmly attached to the leading end portion of the magnetic tape, or a relatively hard plastic leader tape with an engagement bore at the leading end is joined to the leading end portion of the magnetic tape. On the other hand, a drive unit is constructed so that loading or unloading (pulling-out or rewinding) of the magnetic tape is performed by holding and pulling out the leader member or the leading end of the leader tape with a holding member provided in the recording-reproducing unit.
However, when performing the load and unload operations by pulling out the magnetic tape to the magnetic recording-reproducing unit and then winding the leading end on the machine reel of the magnetic recording-reproducing unit, the leading end portion is contacted with tape guides, a magnetic head, etc., and is pulled without being positioned accurately. Because of this, since the leading end portion is easily damaged, it is preferable to reinforce the leading end portion. Leader tape whose strength is higher than that of the magnetic tape can be joined to the leading end of the magnetic tape.
A material that is used as the leader tape is generally a plastic tape which is thicker than magnetic tape. However, the plastic material is easily charged with static electricity by friction, etc., and therefore there is a fear that the magnetic head will be damaged by this static electricity. Particularly, the newer magnetic heads for magnetic recording and reproduction are likely to be damaged by static electricity, because high-sensitivity magnetic heads such as an MR head, etc., are used to obtain high recording density.
In addition, to increase the recording quantity per unit volume of the magnetic tape, recording density is enhanced and there is a tendency to use thin tape. Because of this, tape strength is reduced, the tape edge is likely to be damaged by contact with the flange portions of tape guides during load and unload operations, and there is a fear that tape will be cut by repeated use. Furthermore, there is a fear that the first part of the magnetic tape to be wound on the machine reel of the magnetic recording-reproducing unit will also be damaged when bent and that the strength of that part will be reduced.
On the other hand, in the case where a leader member such as a leader pin, etc., is joined directly to the leading end of magnetic tape to pull out the magnetic tape, the surface roughness will become small, if the magnetic tape is reduced in thickness to meet the high-density requirement, as previously stated. Because of this, the tape surface becomes flat and smooth, the friction coefficient becomes low, and it is difficult to obtain sufficient clamping force between the magnetic tape and the leader member. Thus, there is a fear that the clamping force will be reduced and therefore the leader member will be disengaged from the magnetic tape. Furthermore, in the case where addition of a lubricant to the magnetic layer of the magnetic tape, or application of a lubricant to the tape surface, has been performed to reduce friction between the magnetic tape and the magnetic head, there are cases where the clamping force between the magnetic tape and the clamp member is reduced. In the case where, in view of the points mentioned above, a leader tape is joined to the leading end of the magnetic tape to assure strength, a stepped portion corresponding to a difference in thickness between them occurs in the joint portion between the magnetic tape and the leader tape. If the magnetic tape is successively wound on the stepped portion when wound on the machine reel, a deformation of the magnetic tape called “tape transfer” will occur along the shape of the stepped portion and the contacted state of the magnetic tape with respect to the magnetic head will change. This causes a dropout phenomenon in which suitable writing and reading of data cannot be performed, and results in defects in magnetic recording quality. Generally, magnetic recording is not performed at the tape end region where the aforementioned tape transfer tends to occur. However, if this region is long, recording capacity will be reduced.
The present invention has been made in view of the points mentioned above. Accordingly, it is a second object of the present invention to provide a magnetic tape cartridge that is equipped with a leader tape having characteristics which are satisfactory in strength and other points, to assure reliability.